1. Field of the Invention
The present invention relates to a measurement system utilizing ultrasonic waves for measuring the attenuation characteristics of internal structures, such as organs within the human body, and particularly to a measurement method and system utilizing ultrasonic waves for diagnosis of the internal organs of a human body.
2. Description of the Prior Art
In the field of medical diagnostic technology and metal flaw detector technology, etc., ultrasonic wave image technology is widely employed, wherein the condition of a domain, for example, the location of the boundary from the beam transmitting location is displayed by transmitting the ultrasonic wave beam to an object and receiving and analyzing the wave reflected from the boundary of a domain within an object. The transmitted wave is attenuated in accordance with the internal structure characteristics of an object and is returned as the reflected wave after being influenced so as to contain characteristics indicative of the reflective coefficient of the boundary. Therefore, the attenuation characteristics of the internal structure can be measured by analyzing such a reflected wave in relation to the transmitted wave. Such technology is introduced in the Japanese Laid-Open Patent Specification No. 49-38490 (corresponding to Japanese Published Patent Specification No. 56-37820) or Japanese Published Patent Specification No. 52-24798. These prior art examples disclose that ultrasonic waves having a plurality of frequencies are emitted, the sonic pressure of each frequency is obtained from the received reflected wave, and then the attenuation characteristics of the internal structure are obtained from the ratio of such sonic pressures. However, with respect to the sonic pressure ratio, a large amount of error is usually introduced. That is, in these prior art examples, the phases of each component of the reflected wave differ when these are received from a heterogeneous medium such as a human body, and errors are included in the reflected wave received resulting from the so-called phase cancellation. Therefore, these prior art examples have the problem that an accurate attenuation characteristic cannot still be obtained even by the sonic pressure ratio.